FEMS Microbiology Letters, 362, 2015, fnv056

doi: 10.1093/femsle/fnv056Advance Access Publication Date: 6 April 2015Research Letter

RESEARCH LETTER –Professional Development

van Leeuwenhoek microscopes—where are they now?Lesley A. Robertson∗

Department of Biotechnology, Delft University of Technology, 2628 BC, Delft, the Netherlands∗Corresponding author: Department of Biotechnology, Delft University of Technology, 2628 BC, Delft, the Netherlands. Tel: +31-15-2782421;E-mail: l.a.robertson@tudelft.nlOne sentence summary: The story and fate of van Leeuwenhoek’s microscopes and other lenses as revealed by primary and historical secondarydocuments are reviewed.Editor: Rich Boden

ABSTRACTWhen Antonie van Leeuwenhoek died, he left over 500 simple microscopes, aalkijkers (an adaption of his microscope toallow the examination of blood circulation in the tails of small eels) and lenses, yet now there are only 10 microscopes witha claim to being authentic, one possible aalkijker and six lenses. He made microscopes with more than one lens, andpossibly three forms of the aalkijker. This paper attempts to establish exactly what he left and trace the fate of some of theothers using the earliest possible documents and publications.

Keywords: single lens microscopes; aalkijker; auction catalogue; biohistory

INTRODUCTIONOpticalmicroscopes seem to have developed along parallel lines.Modern compound instruments are claimed to be derived fromthe two-lensed tube invented by the Jansens towards the endof the 16th century (Harting 1850). It is ironic that some of themost significant discoveries in microscopy were made using thesimpler, single lens version which probably developed from themagnifying glasses of Roger Bacon in the 13th century (Clay andCourt 1932). Antonie van Leeuwenhoek was not the only personmaking and using single-lensedmicroscopes, although his werethe simplest (see, for example, the review by van Cittert 1934aand Robert Hooke (1665) described one in the introduction toMi-crographia). Making the lenses stronger alsomade them smallerand there is little difference between magnifying glasses andvan Leeuwenhoek microscopes other than magnifying power.

‘Little animals’ were reported by others after van Leeuwen-hoek’s first descriptions. Despite his speculation about the wis-dom of washing glasses and crockery in canal water contain-ing little animals, and his idea that they might be the sourceof the microorganisms found in the mouth (van Leeuwenhoek1713), he does not seem to have connected his little animalswith illness. However, during his lifetime others were consid-

ering the implications and suggesting that his ‘little animals’might cause diseases. These suggestions were largely ignored.In 1677, ‘an observing person in the county’ commented on re-cent letters in the Philosophical Transactions to the Royal So-ciety (Anon 1677). He suggested that the discoveries of Mr vanLeeuwenhoek implied that the air is also full of little animals.Periods of infection might be associated with periods of calm,east winds or humidity. In Slare (1683), he, when working ona cattle plague in Switzerland, that had Mr van Leeuwenhoekbeen there, he would have discovered some strange ‘insect’ orother. In CH (1702), he described his experiments to repeat vanLeeuwenhoek’s work. His pepper water experiments produced‘capillary worms’ which seem to correspond with van Leeuwen-hoek’s bacteria. He then investigated the water draining froma dung heap, commenting that the microbial community wasricher than in his pepper water samples.

For broader reviews of early microscopes and methods see,for example, Mayall (1886a,b), Clay and Court (1932), Ruestow(1996) and Fournier (1991). Meyer (1937) reviewed van Leeuwen-hoek’s methods.

Many compound microscopes, including Robert Hooke’s,have survived, unlike the simpler microscopes of van Leeuwen-hoek, possibly because the former are more obviously valuable.

Received: 23 February 2015; Accepted: 30 March 2015C⃝ FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

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This article will review what is known about the fate of vanLeeuwenhoek’s microscopes and lenses, using primary and veryearly secondary sources that have becomemore readily accessi-ble with electronic access to catalogues and archives.

The fate of the microscopes and other magnifiers

When he died, van Leeuwenhoek left about 500 microscopesand lenses. Apparently, he preferred to glue a good preparationonto a microscope pin and then make a new microscope. Hismethod of preparing his biconvex lenses has long been debated(e.g. Cohen 1937; Kingma Boltjes 1941), but it seems likely that heused different techniques, depending on his need. If he copiedHooke’s method of melting glass rods to produce glass spheres,those lenses have not survived (Hooke 1665). Only one of the sur-viving lenses appears to have been blown (Engelsman 1983), theotherswere ground and polished. In van Leeuwenhoek (1694), hewrote that his glass blowing skills were limited, having learnedby watching a demonstration by a glass blower at a fair in Delft.

Most of van Leeuwenhoek’s microscopes were the familiartiny, single-lensed, brass or silver microscopes. However, thedrawing published by von Uffenbach (1754) after his visit to vanLeeuwenhoek shows a microscope with two lenses side by side.In one portrait, Verkolije showed him holding amicroscope withthree lenses in a row. Two and three-lensed microscopes alsofeature in the catalogue (e.g. Fig. 1C) for the auction of his mi-croscopes (see below). This arrangement might be to allow theuse of more than one magnification to study a sample. It is verydifficult to transfer fragile samples between microscopes.

AalkijkersIn 1689, van Leeuwenhoek reported that he hadmodified hismi-croscope to allow the examination of the circulation of the bloodin the tails of young eels, tadpoles and small fish. Various trans-lated names have been used for this modification, including eel-spy glass, aquatic microscope, water microscope and fish glass.For simplicity, this paper will use the shortest name, his ownterm—‘aalkijker’. Note thatwhile ‘Figure’ refers to the numberedpictures in this paper, ‘fig’ refers to the notation of the engraveron the original version of Fig. 2A.

The aalkijker consisted of a metal frame (Fig. 2A, fig 9) thatcould hold a glass tube with a living specimen inserted headdown in water (Fig. 2A, fig 13). The frame could either be usedwith one of his normal microscope plates (Fig. 2A, figs 8 and 10),or with a smaller lens holder (Fig. 2A, figs 11 and 12) whichmightbe more convenient with weaker lenses. At the time of writing,no examples of the earlier version are known to have survived.The nearest is a copy attributed to Mayall (catalogue 45541) inthe Oxford Museum of the History of Science. In van Leeuwen-hoek (1708), he mentioned that he had redesigned his aalkijkerto make observations easier, but he did not provide an illustra-tion. Fortunately, vonUffenbach (1754) provided a drawing of themodified version (Fig. 2B), which can also be seen on the fron-tispiece of the auction catalogue (Fig. 1B).

Another aalkijker version attributed to van Leeuwenhoek canbe seen at the Museum Boerhaave in Leiden (Fig. 2C). The tubeholder is shorter and the lens holder is permanently attachedwith detachable lenses. This version is similar to one attributedto van Musschenbroek from around the same time (MuseumBoerhaave catalogue number V07005).

The auction catalogue (Rees 1747) lists three types of aalki-jker (Table 1). Someweremade of silver or brasswith a glass tubeto observe the circulation of the blood (corresponding to Fig. 2A,fig 3). Two copper examples were square (Fig. 2B). Others withglass tubes were described as ‘small’, one of which contained

Figure 1. Frontispiece from the catalogue for the sale of the microscopes (Rees1747). (A) original aalkijker; (B) newest form of aalkijker; (C) three-lensed micro-scope; (D) magnifying glass; (E) loose lenses; (F) tweezers; (G) quill pen and ink;(H) possibly microscope with weaker lens; (I) bound book.

oyster embryos. van Seters (1933) suggested that this could re-fer to capillaries as von Uffenbach (1754) reported seeing oysterembryos in one.

The auctionTwo years after Maria van Leeuwenhoek (1656–1745) died, herfather’s collection of microscopes was sold by auction at the StLucas Gilde in Delft. Two versions of the catalogue have survived(Rees 1747). One has the text in Dutch and Latin, the other showsthe Dutch text and the name of the buyer with the price. Thecatalogue was described extensively by van Seters (1933), so it isonly summarized here. There were 196 microscopy lots, manycontaining two microscopes per box, as van Leeuwenhoek hadleft them (Table 1). Some lots were sets of lenses. As well as thebrass and silvermicroscopes, the catalogue also lists threemadeof gold and a few with lenses made of quartz or sand. The aalki-jkers were sold singly. Nothing is said about the strengths of thevarious lenses, but samples are mentioned.

At first glance, the illustration at the front of the auction cat-alogue (Fig. 1) seems rather fanciful, but closer examination al-lows the identification of sale items. Two forms of the aalki-jker are shown (A and B), as is a microscope with three lenses(C). The small magnifying glasses (D) are mentioned separately(as fire glasses) in the inventory of the van Leeuwenhoek house(Geesteranis 1745). The auction catalogue includes a number of

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Figure 2. The aalkijker. Where an item is referred to as ‘fig’ rather than ‘Figure’, it refers to the original notation by the engraver on the picture. (A) The original aalkijker(van Leeuwenhoek 1689), showing it with the microscope plate fitted (fig 10), additional lenses (fig 11, fig 12) and its constituent parts. (B) Drawings of the updatedaalkijker (von Uffenbach 1754). (a) glass plate; (b) brass plate; (c and f) retaining brass strips; (d) microscope mount; (e) microscope plate. (C) The aalkijker held byMuseum Boerhaave in Leiden (catalogue number V07015) and a red lens case (catalogue number V07016) top left. Inset, lenses for the aalkijker (also V07016).

lenses, presumably indicated by the round items in the trays(E). Other items were in common use [e.g. quill pen and ink (G),book (I)], and similar tweezers (F) have survived and are in Lei-den’s Museum Boerhaave. The item (H) just to the right of theengravers signature is interesting. It appears to be the samplepin and adjusting screws from a microscope, but with a largerlens. This would provide a useful transition between magnify-ing glasses and the stronger lenses of the microscopes while al-lowing control of the sample’s position and focus. The lacqueredcabinets for storing the microscopes in the front hall of the vanLeeuwenhoek house were also sold (Rees 1747).

Most of the buyers were Delft residents, and quite a fewwerenotaries. Some people bought large numbers of microscopes,most notably Willem Vlaerdingerwout (notary), who bought 20lots and two of the cabinets, and Hendrick Halder (notary; 18lots and two cabinets). The auctioneer, Adriaan Rees, bought theonly gold microscope that sold (two others were withdrawn).

Others who bought multiple lots included Hendrik Verbrugge(coppersmith), Matthys van den Briel (seafarer), Willem Ouwens(doctor), Cornelis de Vegter (surgeon) and Baroness van Reede,among others. Dobell (1932) was surprised that the buyers wereso local, but the sale happened long after van Leeuwenhoek’sdeath,most of his friendswere dead, andmicroscopyhadmovedon.

With the exception of the 10 microscopes discussed below(Fig. 3, Table 2), all of van Leeuwenhoek’s original microscopeshave disappeared. Two others are only known from photographs(Penso and Rampa 1981; van Zuylen 1981), but seem to have sur-vived into the 20th century.

The Royal Society of Londonvan Leeuwenhoek selected 26 of his microscopes to be given tothe Royal Society after his death. They were described in de-tail by Folkes (1722) and Baker (1739). All were made of silver

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Table 1. Summary of the microscopes auctioned after the death ofMaria van Leeuwenhoek (Rees 1747). Where used, ‘fig(s)’ refers to theengraver’s notation on the original of Figure 2(A) and not the numberof a Figure.

Metal Lens materialNumberof lenses

Numberof micro-scopes

MicroscopesBrass Glass 1 96Brass Glass 1 881

Silver Rock crystal 1 4Silver Sand 1 2Silver Glass 1 120Silver Glass 2 3Silver Glass 3 2Brass & silver Glass 1 1Brass & silver Glass 2 3Gold Glass 1 3Total microscopes 322AalkijkersSquare2, brass 2Brass,3 glass tube 6Small3, brass, glass tube 11Silver, glass tube 3Brass & silver, glass tube 1Total aalkijkers 23Lenses in brass holders4 Glass 172

1The description uses the diminutive of the word used for the othermicroscopesand with an attached dish. It could refer to the basic microscope structure, butwith the dish-like lens holders shown in the engraver’s notation as figs 11 and12 in Figure 2A in place of microscope plates. It might be the magnifier shown atH in Figure 1.2See Figure 2B.3See Figure 2A.4 See insert in Figure 2C. Alternatively, they could be un-mounted microscopeplates (fig 8 in Figure 2A).

reportedly extracted from the ore by van Leeuwenhoek himself(Schierbeek 1947), with a range of magnifications (Table 3). Theywere arranged two to a box in drawers in a small cabinet, andoriginally had mounted samples. In a later publication, Baker(1754) rather indignantly wrote that several writers were claim-ing that Mr van Leeuwenhoek used globules or spheres of glass,but they obviously hadn’t seen the microscopes. As he wrote hisarticle, the microscopes given to the Royal Society were stand-ing on his table and every one of them had a biconvex lens, not asphere. It might be speculated that this was why van Leeuwen-hoek was more successful with the single-lens microscope thanothers who used spheres.

Sadly, these microscopes disappeared in the first half of the19th century. In 1855, Sir James South wrote to the Royal Societyasking for an investigation into their loss (quoted in Ford 1983),but this came to nothing. The last person known to have bor-rowed them was Sir Everard Home (Clay and Court 1932), andthere is no record of their having been seen again. It has beensuggested that the van Leeuwenhoek microscopes might havebeen destroyed in the fire at Sir Everard’s home that destroyedmany of the papers of his late brother-in-law, Sir John Hunter(Clift 1834; Anon 1904; Livesley and Pentelow 1978).

GiftsAntonie van Leeuwenhoek never sold his microscopes. Indeed,despite the very high ranks of some of his visitors (Backer et al.2014), there are only two cases where it is suggested that he gavemicroscopes away.

Figure 3. Microscopes with a claim to be surviving authentic van Leeuwenhoekmicroscopes (see Table 2). [Images (A–I) with permission from Museum Boer-haave, Leiden].

Folkes (1722) described a visit to Delft by Queen Mary, wifeof William of Orange when, impressed by her interest, vanLeeuwenhoek gave her two of his microscopes. Folkes said thatan acquaintance had had Queen Mary’s microscopes ‘in hishands for some time’, providing evidence that the gift had beenmade. However, these microscopes cannot be found. The sci-entific instruments held by the Royal Collection in Britain weretransferred to the British Museum and thence to London’s Sci-ence Museum, but the microscopes are not there. Accordingto Clay and Court (1932), in the late 19th century, Sir FrankCrisp was building an extensive collection of microscopes withthe intention of presenting them to the British Nation. He wastherefore allowed to remove the microscopes from the ‘GeorgeIII collection’ in Kings College, where they had been placed byQueen Victoria. Sadly, he didn’t mention this planned gift in hiswill. After his death ‘the Crisp collection’, including the micro-scopes from the George III collection, was sold by auctions in1923–1925 (Anon 1925; Gunther 1925). This collection included avan Leeuwenhoekmicroscope, which seems likely to have comefrom the Queen Mary gift. It hasn’t been seen since. The auctionhouse and its records were destroyed by bombing during WorldWar II.

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Table 2. The surviving microscopes and lenses for the aalkijker (an apparatus for examining the circulation of the blood in the tails of livingeels, tadpoles and fish).

Microscope MetalFocal length(mm) Magnification Location

A1 Brass 2.12 118 Bought by Dirk Haaxman at theoriginal auction, now MuseumBoerhaave, Leiden.

B1 Brass 3.39 74 Bought by Dirk Haaxman at theoriginal auction, now privatecollection.

C1 Brass 0.94 266 University Museum, UtrechtD1 Brass 2.28 110 Natural History Museum, AntwerpE1 Brass 2.24 112 Deutches Museum, MunichF1 Silver 3.31 80 Museum Boerhaave, LeidenG1 Silver 3.61 69 Previously private collection,

unknown since an auction atChristie’s in 2009

H1 Brass no lens Bought by Dirk Haaxman at theoriginal auction, previously atDelft University of Technology,since 1983 in Museum Boerhaave,Leiden

I1 Brass 1.5 167 Deutches Museum, MunichJ1 Silver 3.66 68 Private ownership until 1983 when

donated to Museum Boerhaave,Leiden (Fournier 2002)

Lens 12 Brass 8 32 Museum Boerhaave, LeidenLens 22 Brass 5 50 Museum Boerhaave, LeidenLens 32 Brass 5 50 Museum Boerhaave, LeidenLens 42 Brass 3.8 65 Museum Boerhaave, LeidenLens 52 Brass 1.9 150 Museum Boerhaave, Leiden

1see Figure 3.2see Figure 2C.

Table 3. Baker’s measurements of the Royal Society microscopes(Baker 1739), recalculated to metric units and an eye distance of 250mm, for comparison with Table 2.

Number ofmicroscopes Metal

Focal length(f) (mm) Magnification

1 Silver 1.27 2001 Silver 1.52 1661 Silver 1.78 1433 Silver 2.03 1253 Silver 2.28 1118 Silver 2.54 1002 Silver 2.79 903 Silver 3.05 832 Silver 3.55 711 Silver 3.81 661 Silver 5.08 50

In 1697, Peter the Great invited van Leeuwenhoek to visit theboat on which he was travelling to explain his discoveries. It isfrequently claimed that van Leeuwenhoek gave the Czar micro-scopes and one of his aalkijkers. However, there is nomention ofthis gift in the account of the meeting written by a friend of vanLeeuwenhoek’s, even though his parting with one or more mi-croscopes would have been a remarkable event (van Loon 1731).The claim seems to be based on Haaxman’s story (Haaxman1875; Crommelin 1926) that a Professor deGorter (probablyDavid

de Gorter, Royal Physician to Elizabeth, Empress of Russia) hadbrought a microscope, lenses in a red morocco case with ‘Anth.Van Leeuwenhoek’ on the lid, and an aalkijker fromRussia. How-ever, there is no evidence to link the two events which happenedalmost 200 years apart. It might (as speculated by Dobell 1932)have happened, but de Gorter’s microscopes might equally eas-ily have come from the auction, although the catalogue does notmention a red morocco case.

The surviving microscopesNine van Leeuwenhoek microscopes with claims to be authen-tic were assembled for the ‘Beads of Glass’ exhibition (Bracegir-dle 1983). These microscopes, together with a tenth acquired bythe BoerhaaveMuseum in Leiden during the exhibition (Fournier2002), are the 10 known survivors shown in Fig. 3 and Table 2.Three of them (A, B and H in Fig. 3) previously belonged to theHaaxman family (relatives of van Leeuwenhoek), having beenbought by Dirk Haaxman at the auction (Rees 1747; Rooseboom1939) and retained by the family until the 20th century. Noneof the other microscopes can be traced back to specific auctionlots, and the provenance of several can only be tracked to the19th century.

MicroscopeH (Fig. 3)was, for a time, exhibited in the entrancehall of Delft University of Technology’s Microbiology Laboratory,but it has been in the greater security of Leiden’s Museum Boer-haave since 1983 (Bracegirdle 1983), and a copy has taken itsplace in Delft.

Like the Royal Societymicroscopes, all survivingmicroscopeshave biconvex lenses (van Cittert 1932, 1933, 1934b; Engelsman

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1983; van Seters 1933) and have all lost their samples. Only a fewof van Leeuwenhoek’s samples have survived (Dobell 1932; Cole1937a,b; Ford 1981).

Microscope copiesCopying a van Leeuwenhoek microscope is relatively simple.Since they are simply hand made from metal and glass, it is dif-ficult to be certain of the provenance of a microscope unless ithas supporting documentation or auction or assay marks. Onthe rare occasions when they appear, newly discovered micro-scopes are generally compared to known examples. If they donot match a knownmicroscope, they are possibly authentic. Mi-croscopes A and C in Fig. 3 seem to have been the most fre-quently copied. Where the maker and date are known, copiessuch as those made of the Utrecht microscope by John Mayall(Crisp 1886; van Zuylen 1981) have acquiredmuseum status (e.g.items 45541 and Wh.1817 in the catalogues of Cambridge’s Mu-seum of the History of Science and the Whipple Museum, re-spectively). Modern copies are often, but not always, marked(e.g. catalogue number 1929–802 at London’s Science Museum,and 41858 in Cambridge). Instructions for making copies areavailable on the internet, and some people are making them forsale. However, some of these copies have a glass sphere as alens, limiting their use. At the time of writing, Museum Boer-haave in Leiden is selling copies of one of their microscopeswith lenses intended for mobile phones, thereby making themuseable.

Copies of the microscopes with good quality lenses can befound (e.g. Loncke 2006a,b), and it is possible to repeat someof van Leeuwenhoek’s experiments (Robertson 2015). Combinedwith a modern digital camera, it is even possible to make pho-tographs and film clips (Robertson 2014).

CONCLUSIONAt first glance, it might seem unreasonable that around 500 mi-croscopes and lenses have vanished. Some microscopes wereprobably discarded by heirs who didn’t know what they were, orthought that they were outdated. The gold and silver ones wereprobably melted down. Others were obviously re-sold, and a fewhave appeared in later inventories of other estates, only to van-ish again. Abram Edens, the man who delivered van Leeuwen-hoek’s bequest to the Royal Society (Rusnock 1996), bought 10brass and two silver microscopes at the auction, as well as oneof the modified aalkijkers and a set of lenses, but the inventoryof his own estate only lists three microscopes and eight lenses(Anon 1765). In 1753, Jan Arnold van Orsoy left one brass andfour silver microscopes which were sold to men recorded onlyas Jongerhelt and Tilenburg (Anon 1754). In 1758, Aron de Pintoleft one (Anon 1785). As late as 1823, Pieter van Buren left oneamong his collection of curiosities (Anon 1823).

The microscopes are tiny, the mounted lenses even smaller,and who could have predicted that such unprepossessing thingswere important and would eventually become so valuable andshould be treated with care? In 2009, a silver van Leeuwenhoekmicroscope (Fig. 3G) sold at auction for€350 000, and it is tempt-ing to think that the publicity surrounding the sale would haveencouraged owners of previously unrecognized microscopes tocome forward. Microscope J in Fig. 3 came to light after its ownervisited the ‘Beads of Glass’ exhibition in Leiden and learnedwhat it was (Fournier 2002)—could there still be more outthere?

ACKNOWLEDGEMENTSThe author would like to thank all the archivists and curatorswho made this search possible.

Conflict of interest. None declared.

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